How to Un-Clog an Air Conditioning or Heat Pump Condensate Drain to Avoid Leaks & Damage

A clogged condensate drain can cause air conditioner problems or even loss of cooling

Condensate may overflow into the building, causing water damage or even a costly mold contamination problem

Condensate that fails to make it through a clogged drain line may spill into a condensate overflow pan that uses a sensor switch (instead of a second condensate drain line) to turn off the entire air conditioning system rather than risk leak damage.
SeeCONDENSATE PAN SWITCH LOCKOUT

Clogged condensate may accumulate in a location where it breeds bacteria, other pathogens, or even mosquitoes.

What Causes A/C Condensate Drain Line Clogging?

A/C or heat pump condensate drains can become clogged, leading to condensate leaks, spillage, or even bacterial hazards in a building.

Clogged air conditioner condensate drain lines can form another source of air conditioner or heat pump condensate leakage that can in turn lead to hidden water damage or in some locations an indoor mold problem or bacterial contamination.

Our photograph of a nearly full A/C condensate overflow pan (at left) shows what can happen if the primary condensate air conditioner condensate drain line is clogged and worse, the condensate drain overflow pan is also itself clogged and not draining properly. Luckily we caught this attic mold and bacterial pond before it had soaked the ceilings below.

We see air conditioner or heat pump condensate drain lines clogging for several reasons:

Condensate trap debris dry-out cycle: Dust and debris or nearby insulation entering the condensate drain line trap near the air handler, often where the trap design includes a vertical standpipe open to the air, serving as an emergency overflow to prevent condensate from backing up inside the air handler itself.

In months during which an air conditioning system is not in use, particularly for non-heat-pump systems that perform cooling-only, condensate and accumulated dust and debris that was resting in the condensate drain trap can convert to a dried plug of crud as the water portion of the condensate evaporates.

After several years of this wet, sludge accumulation, and then drying cycle, the plug of dried sludge in a condensate trap or drain can actually block condensate flow through the system.

Improperly-installed condensate drain lines with a long near-horizontal run can allow dust and debris to accumulate, dry, and ultimately block condensate flow in the drain line

Insects, insect nests, or on larger piping systems, even rodents can clog a condensate drain line.

Condensate overflow pan drain blockage: dust and debris also accumulate readily in a condensate overflow pan where it can flow to and block the opening to the overflow pan's independent condensate drain line. If a blockage occurs here, the condensate overflow pan may not do its job of preventing condensate spillage into the building. (Ref. Uniform Mechanical Code
Sec. 1205 and Sec. 510. Condensate overflow pan is suggested for attic space per UMC (Uniform Mechanical Code) Section 1205.)

How do I Clean an Air Conditioning or Heat Pump Condensate Drain?

Remove visible debris from the clogged air conditioning or heat pump condensate drain: start with a simple visual inspection. You may see a plug of crud blocking a condensate overflow pan right at its drain inlet - material that can be manually removed and the area wiped clean.

Peering into the standpipe at a condensate drain trap, you may see crud right in that area that can be fished out or simply loosened and flushed through the drain line by working carefully so as not to break or loosen any pipe connections.

Our photo (left) shows a poorly-installed A/C condensate drain system: the air handler condensate drain is installed in common with the overflow pan drain line - so that a blockage in the condensate drain line will guarantee that condensate spills onto the attic floor.

The A/C condensate tray should have either had its own independent drain line, or it should have been installed with a sensor switch that shuts down the A/C or heat pump system if spillage is detected in the overflow pan. Finally, there is no trap on the condensate line and no air vent.

Snake the clogged A/C condensate line carefully using a condensate drain brush or plastic tube: We've loosened and freed a clogged condensate drain line by simply snaking the line gently with a piece of plastic tubing inserted at the trap vent and pushed through the condensate trap.

Remember that because condensate drain piping is usually 3/4" plastic piping you don't want to use unnecessary force that could result in breaking any pipe or causing a leak at a connection. Gently does the trick most of the time.

Our photo (left) shows the trap at a condensate drain pipe right at the air handler. Notice those three red plastic caps? Each of those is an access port through which this air conditioning condensate trap and drain can be quickly and inexpensively cleaned.

Notice that small black bristle brush clipped to the upper red cap in the center of our photo. The brush has a flexible blue plastic handle, allowing the homeowner or A/C heat pump service technician to easily push the brush through the trap and drain line to clean it.

Because most A/C condensate drain clogs occur right at the trap, this is the quickest, easiest, lowest-cost method to clean and clear an A/C or heat pump condensate drain clog. Air conditioner / heat pump condensate traps with cleanout ports can be cleaned using soapy water and the manufacturer-provided cleaning brush. Some models can be easily disassembled for further cleaning of internal parts.

Condensate traps that include cleanout caps include the EZT-150 EZ-Trap and UltraTrap (sketch at left) that work on both positive or negative pressure air handlers. Below we provide a link to installation instructions for the condensate drain trap provided by AirTech Products shown at left.

Using a plumbing snake to clear a condensate line: In some cases a clog might occur in an A/C - heat pump condensate drain that is beyond the reach of your drain cleaning brush.

Try a longer length of flexible plastic tubing as a gentle condensate drain snake, use a small plumbing drain snake, or try the remaining A/C condensate drain clog clearing methods listed below. For long condensate drain line runs, you may need to install additional cleanout ports in the line such as the EasyKlear cleanout port discussed just below.

Using a CO2 cartridge to blast out a clogged A/C or heat pump condensate drain line is a method followed by some service techs. Heating or air conditioning equipment suppliers sell a small CO2 cartridge canister with an outlet adapter and fittings to connect to various sizes of piping.

The canister is connected to the condensate drain line inlet (and the vent at the drain plugged with an expandable rubber plug sold for that purpose).

A CO2 cartridge is dropped into the canister and its cap screwed on. Screwing the canister top on tightly will puncture the CO2 cartridge, sending a quick shot of high pressure gas through the drain line, clearing an obstruction. (This method is also widely used by oil heat service technicians to clear a clogged heating oil line.)

Vacuum clean the clogged condensate drain line: Use a manual pump to vacuum clean a clogged air conditioning or heat pump condensate drain line. The pump inlet side is connected by an adapter fitting to the condensate drain line opening.

You'll have to plug the nearby vertical standpipe at the condensate trap if one is provided. The manual condensate drain line pump's outlet side is connected to a hose run into a bucket or a nearby building drain to receive any waste.

Little Giant Condenate Drain Pump. In December 2014 the company's website was not working but their products are widely available from plumbing and HVAC suppliers. Quoting from Fraknlin-Electric, a supplier of Little Giant pumps, "Little Giant condensate removal pumps are engineered for a wide range of specific air conditioning, refrigeration, and heating applications, as well as may other automatic drain uses." - http://www.franklin-electric.com/hvac/condensate-removal.aspx

Mighty Pump - we removed the live link for this product after a reader reported that the recommendation for this device was posted by Stuart Oakner the owner of the company who posted suggestions without so identifying himself. Details are at FAQs in this article.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.

We like the clogged condensate drain vacuum cleaning approach better than the blow-out approach if we can get this method to work because it is more gentle, reducing the risk of damaged piping, and because we minimize the risk of blowing a plug of crud downstream to a more distant location where it can form a new clog or plug in a long condensate piping run.

[Click to enlarge any image]

Several air conditioning and plumbing suppliers provide easy-to-clean air conditioning condensate cleanout ports such as the one shown above, including the Easy Klear condensate line cleanout (photo at left) that is particularly useful if your condensate drain line has a long run with a slope of less than 1/8" per foot.

This A/C or heat pump condensate drain line cleanout is intended to be vacuumed using a connection to a shop vac.

Blow out the clogged condensate drain line: Use a compressed air source or a manual pump such as the Mighty Pump (safer) to try blowing out the clogged air conditioning or heat pump condensate drain line and trap.

Using a manual pump, the pump's outlet end is connected to the condensate drain opening or standpipe, any other nearby openings are plugged, and you use the pump to try to force the blockage through the system to an outlet. This approach works best if the condensate drain line is actually fully clogged and full of standing water or condensate.

WATCH OUT: using high pressure to try to blow out a clogged drain pipe of any kind can result in damaging the drain piping, causing it to break or come disconnected, spilling ugly condensate and crud all over. This risk is greatest if the original piping connections were not properly glued or were not soundly made in the first place.

The Jones JV1 blow out valve product is a plastic valve that includes a flare fitting that will allow the connection of a CO2 or Nitrogen tank of compressed gas used to "blow out" the condensate line clog.

The valve attaches to a 3/4" condensate drain line and provides a 1/4" male flare fitting that incorporates a "one-way" internal Schrader valve to permit air to blow into the valve but won't leak out.

The Jones Valve is a simple condensate blow-out valve that is inexpensive and easy to use. Simply attach your nitrogen or compressed air tank hose to the 1/4" flare fitting on the Jones Valve, turn the handle 90°, and open the gas slowly to the line. Turn the handle 180° and clear out the other side of the line. Make sure the arrow (indicating air port) is pointing to the back side of the Jones Valve after service is complete.

All-Access condensate drain line cleanout device, MSD Research, Inc., Boca Raton, FL 33428, Email: Sales@MSDResearch.net,
Website: http://allaccessdevice.com, provides a condensate drain line fitting that permits connection to a wet-vac or to an air (or gas) pressure source to remove blockages without having to cut the condensate drain line apart.

Thanks to All-Access for notifying us of condensate drain maintenance requirement updates in the ICC IMC 307.2.5 & IRC M1411.3.3 Drain Line Maintenance code for 2015. That code is discussed at CONDENSATE DRAINS

Watch out: Cleaning out partly-blocked, sluggish A/C or heat pump condensate lines: neither the vacuum method nor the blow-out method will work very well for cleaning a sluggish condensate line that is not totally blocked, since you may simply move air past the blockage rather than removing it.

If you encounter this problem, try hooking up your pump in the "blow-out" configuration, then try filling the condensate line with tap water so that the pump pressure can act mechanically on the clog.

Watch out: connecting a blow-out device or a vacuum device to a condensate drain that is connected to building plumbing drain waste or vent piping may cause some trouble.

These devices should work well for condensate drains directed to the building exterior but depending on piping arrangement (and eschewing for a moment the fact that DWV connections of condensate drains are not recommended without an air gap) using a shop vac you may pull wastewater or even sewage back into the condensate drain.

Frequently Asked Questions (FAQs)

Reader comments:

(May 13, 2011) Chris Nallie-Courtney said: Thank you! This was very helpful. I was able to clean out my drain line myself.

(June 22, 2011) w.m.cutler said: very educational,did all the work myself,replaced trap and cleanout 3/4 pvc,used air and shop vac. system fine now.

(Sept 25, 2011) Rana said:

Thanks so much! I was able to clean out the drain myself rather than take off work to wait for the A/C tech to come out. And I'm happy to know more about the upkeep of my own home.

(June 20, 2014) Linda Vereen said: Learned so much from your site. What a great service you provide.
Love that you post pictures and details, it makes it easy to understand.
thank You

(July 4, 2014) Rance said: Thank you so much for posting the info, etc. on ac condinsate line cleaning and the "proven" options... Tools that you have tried and recommend. Happy and safe 4th of July to you and yours.

(May 1, 2014) Tom Kolter said:

You should check out the Jones Valve, too, available at Supco and Watso, United Refrigeration and Johnstone, the latter two as "Line Drive".

Question: AC water clogs - slope is too great on the drain

(June 23, 2011) Ma Neumann said:

A neighbor in my condo tells me that our #1 problem with the AC is water clogs--when the condensate drain's slope is too great, he says, the water rushes down the pipe and clogs up all by itself, sort of like a vacuum. I can't find any references to water clogs on the Internet. Everything I see about clogs uses terms like sludge, dirt, debris--solid material, not vacuums. Please educate me.

Reply:

Ma Neumann:

Your neighbor's explanation makes no sense to me at all. What clogs A/C condensate lines is typically crud (dust, debris, rust flakes from inside the air handler) that collect in the condensate line trap, or at the condensate drip pan opening that feeds into the condensate line.

Excessive slope is a problem on drain lines on SEWER piping (black water, toilet waste) because if the slope is excessive the water can rush down the drain line leaving solids behind to clog the piping. But on a condensate drain line there is no sewage and no solid waste.

Question:

(July 22, 2011) Frank said:

I noticed leakage in my ceiling after a technician rewired my brand new conditioner to run at a higher fan speed which forced more air into my house. Made sense and now feels cooler. a few hours later is when I noticed the water leak. I went into the attic and can see that there is water in the catch tray but the kicker is that there is a small hole a couple of millimeters round at the end of the tray allowing the water to leak out into the insulation down the roof into my plaster ceiling. What in the world is a hole doing in my catch tray?

Reply:

try a diyvac wet vac attachment to unclog the drain line .The attachment fits on the wet vac and drain line perfectly and takes a couple of minutes to unclog once vacuum is turned on.

Question: water leaking out onto furnace

(May 31, 2012) jay said:

water is coming out the top of my ac furnace

Reply:

Jay, if your unit's condensate drain pan has begun to leak, or if its drain is clogged, those would cause the leakage at the air handler as you described. There should be a removable panel to give view inside the unit to see the condition of the drain pan itself.

Question: AC condensate drains into a bathroom sink P-Trap

(June 26, 2012) Remo said:

Hello, it looks like my condensate drain goes directly from the ac unit down to a nearby bathroom sink and connect to the p trap. there is no way to pour bleach suck with a wet vac. when the AC kicks on, there is a horrible gorgle sound out of our bathroom sink, how can i fix that?

Reply:

Remo, it sounds as if the drain tubing needs to be disconnected and cleaned.

Follow-up

Dan, i think you are right, but how do we disconnect it? at what point, mid way? at the AC

Reply:

I'd start by trying to get inside the air handler (power off) to find the opening into the drain, and to brush clear the trap if one is present.

Question:

(July 7, 2012) M12451 said:

My ac runs but water fills up at the bottom where the condensation pump is located, I not sure what do. Can someone with good expertise please advise.

Thanks Not a HOT Summer

Reply:

M
It sounds as if either the condensate pump switch or the pump itself needs replacement

But first be sure the condensate pump is plugged in and has electrical power

Question:

(July 17, 2012) Ann Borg said:

Our condensate line backed up causing a wet drywall and ceiling....because the builder was too cheap to install an over flow valve. It has been corrected and all of the information on your website was excellent. Thank you.

Reply:

Ann, sorry to read of the condensate backup - but what "flow valve" are you referring to? It is common to drain condensate by gravity when possible, and it is also not uncommon for the condensate drain trap or line to clog with lint and crud - it's a maintenance item. Can you tell us what valve you mean? Do you mean a condensate overflow tray sensor switch?

Question:

(July 27, 2012) Jennifer said:

Hi Our 2 units have only one drain line and it seems to leak. What is the code that each line should have their own independent line?

Reply:

Jennifer, none that I know about. But the condensate drain does need to be large enough to handle the condensate flow rate without backing up; if your condensate line is leaking I suspect either it is clogged or there are improperly made leaky connections.

Question: who do I call to fix a clogged condensate drain

So if one has this issue, do I call an HVAC technician or a plumber?

Reply:

Start with your HVAC tech. who may have just the right sized tools to clear the condensate line clog. But some problems such as a clogged condensate line or a broken condensate pump are within the scope of others such as a plumber, handyman, and many homeowners.

Question: condensate water coming out of the ceiling or leaking onto the floor

(Aug 25, 2012) Rich said:

I noticed yesterday that there was water coming through the ceiling and suspected it was the A/C unit. When I got into the attic there was no water in the drip pan or any evidence that it had been wet, and the drain lines were not clogged (did the water/bleach test and drained properly).

I opened up the unit which held the refrig evap and that inside drip pan was full and I suspect overflowed into box where the ducting is connected. The liner is soaked as well as one ducting had a puddle of water. This is where the damage to the ceiling came from. Do I have a bad refrig evap unit or bad drip pan inside? My first thoughts were we just recently had a lot of humidity and the drip pan couldn't keep up... Thoughts? Thank you!

(Sept 9, 2012) Samantha said:

I'm noticing water dripping from the bottom of our air handler onto the floor (1st story, closet installation). I'd like to clean out the drain pipe as I'm guessing there is a clog, but there isn't any access point - should I just attach a wet vac to the outside pipe and vacuum it out? Our house came with a heil unit and I can't find anywhere to even open it up to view the drain pan itself.

Reply:

To answer this we need to look at the drip pan to see if it's clogged, rusted, perforated, leaking, overflowing, or if there is a problem with the condensate drain piping. Start at the unit.

Question: reader suggests other condensate line cleaners

Tom Kolter said:

You should check out the Jones Valve, too, available at Supco and Watso, United Refrigeration and Johnstone, the latter two as "Line Drive".

Reply:

JV1-Jones Valve Condensate Drain Blow-Out Valve, is available from SUPCO HVAC parts, Website: http://www.supco.com/. Email: orders@supco.com, Tel: 1-800-458-2818
The Jones JV1 blow out valve product is a plastic valve that includes a flare fitting that will allow the connection of a CO2 or Nitrogen tank of compressed gas used to "blow out" the condensate line clog. The valve attaches to a 3/4" condensate drain line and provides a 1/4" male flare fitting that incorporates a "one-way" internal Schrader valve to permit air to blow into the valve but won't leak out.

Question: risks of condensate leaks and what to do

(July 13, 2014) Altin said:

the top ac drainage is leaking, also the bottom. what is the risk and what should I do?

Reply:

Altin

The risk is water damage to the equipment - depending on where condensate is flowing; other risks include mold or other water damage, or bacterial contamination such as Legionnaire's disease.

YOu want the condensate pan fixed if it's leaking, the drain un-clogged and flowing.

Re-posting a reader's comment without disallowed link:

Stuart said:

Never Cut Or Pull Apart Drain Lines once the ALL-ACCESS AA1 is installed.
It provides easy access to clear and maintain drain lines using any method.
Please take a look at allaccessdevice dot com to learn how it works and where it is sold.

Stuart refers to a fitting that is added to the condensate drain to permit drain line cleaning by attaching compressed air, refrigerant, or possibly a vacuum.

Watch out: this fitting and its use may be inappropriate for condensate drains connected to plumbing system piping. - Ed.

Thanks to reader Stuart Oakner for suggesting additional discussion of the Mighty Pump as a less costly way to clear blocked air conditioning or heat pump condensate drains than calling the HVAC service technician.

But, he is the owner & salesman behind both the Mighty Pump and the All-access device. There should be an editorial policy of not allowing product inventors/sales reps or whatever to influence the placement of their own products whether they're professionals or not, at least not without an explicit disclosure.

You can see his affiliation here [references deleted for privacy] - I.H.S. [email on fiile]

Reply:

Thank you for informing us of this. It's a first to have been surprised with a sneak product placement. We will review and edit the document accordingly. Perhaps you could also identify yourself?

Reader follow-up:

I came from another web forum and noticed this guy show up and started pitching his product using third person voice. A web search led me to discover that he's doing the same thing on your site. That's how I stumbled into your page and decided to drop you a line. I think that is enough :)

-ICH

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Easy Klear condensate drain line cleanout valves can be installed anywhere in the run of a condensate drain and include fittings to make cleaning the air conditioner or heat pump drain line simple.

Mighty Pump, is a manual pump that is used to clean or clear out a debris-clogged A/C or heat pump condensate drain. The kit from acdrainpump.com includes a reversible, hand operated pump and flexible inlet and outlet hoses designed along with an adapter to connect the pump to a 3/4" condensate drain line. The company can also be contacted by email to Info@ACDrainPump.com.

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